Hitherto, Metal-Organic Frameworks (MOFs) prepared by three-dimensionally organizing transition metal ions and organic molecules so as to form nano-pores having an ordered size and array have been reported as gas adsorption materials (see, e.g., Non-Patent Documents 1 and 2). Also, a technique of synthesizing one type of MOFs, i.e., Zn4O(2,6-naphthalene dicarboxylate anion)3, in diethylformamide (DEF) and introducing the synthesized MOF to a pressure-tight vessel is proposed (see, e.g., Patent Document 1). Patent Document 1 proposes a method of, after introducing the synthesized MOF to the pressure-tight vessel together with the DEF, replacing the DEF with a solvent (chloroform) which has higher volatility than the DEF and which does not cause phase dissociation with respect to the DEF, and expelling the chloroform from the pressure-tight vessel. With the proposed method, Zn4O(2,6-naphthalene dicarboxylate anion)3 can be filled in the pressure-tight vessel without being exposed to the atmosphere, and the hydrogen-gas adsorption capacity of the MOF can be increased by preventing adsorption of undesired gases (e.g., water vapor) before use. Further, another technique of, after synthesizing the MOF, forming a coating that allows adsorbed gas (e.g., hydrogen) to pass therethrough, but that does not allow undesired gases (e.g., water vapor) to pass therethrough, is proposed to be able to prevent adsorption of the undesired gases (e.g., water vapor) before use and to increase the hydrogen-gas adsorption capacity of the MOF (see, e.g., Patent Document 2).
[Non-Patent Document 1] J. Am. Chem. Soc., 2006, 128, 3494-3495
[Non-Patent Document 2] J. Mater. Chem., 2006, 16, 626-636
[Patent Document 1] Japanese Unexamined Patent Application Publication No. 2006-220168
[Patent Document 2] Japanese Unexamined Patent Application Publication No. 2006-218349